Many of the potential benefits envisioned as a result of the application of recombinant DNA technology to medical problems require the insertion into host organisms of genes able to direct the biosynthesis of required proteins. In most cases a protein of interest will normally be synthesized in animal cells and not naturally found in yeasts or other lower eukaryotes. Although it has been possible to clone a number of different animal genes containing the information necessary to code for proteins, reports of the expression of these proteins in bacteria and other unicellular organisms is limited. Some which have been expressed in E. coli are the human polypeptide hormone somatostatin [Itakura, K., Hirose, T., Crea, R., Riggs, A. D., Heyneker, H. L., Bolivar, F. and Boyer, H. W. (1977) Science 198: 1056-1063], rat proinsulin, and human insulin chains.
Previously we succeeded in expressing the chicken ovalbumin gene in E. coli HB101 by fusing said gene near transcriptional and translational initiation regions. See Proceedings of National Academy of Sciences (1978) 75:5936-5940. Next, we succeeded in expressing the chicken ovalbumin gene in yeast by fusing said gene in the correct orientation relative to a transcriptional initiation region.